This invention relates to hydraulic pumping systems for pumping well fluids, and more particularly to the control of the power fluid flow to the downhole, hydraulically actuated pump.
Hydraulically actuated downhole pumps have been used rather than beam pumping units in many locations. Hydraulic units are especially attractive in deeper and higher producing wells.
A hydraulic pumping system uses an aboveground pump (typically one aboveground triplex pump for each well but a large pump can be used for several wells) to supply pressurized fluid, some of which is used as power fluid to actuate the downhole, hydraulically actuated pump. The downhole pump generally returns at least some of the power fluid, together with produced well fluids. A portion of the total return fluid is then conditioned for use as power fluid. A bypass valve is connected to allow some of the fluid from the aboveground pump to bypass the downhole pump. In the past, this bypass valve has been manually adjusted to vary the speed of the downhole pump to achieve the desired number of strokes per minute.
Hydraulic pumping systems are described in, for example, U.S. Pat. No. 2,046,769, U.S. Pat. No. 2,119,737, and U.S. Pat. No. 2,593,729 issued to Coberly and U.S. Pat. No. 3,709,292 and U.S. Pat. No. 3,782,463 issued to Palmour.